Partial Posttraumatic Stress Disorder (pPTSD) describes trauma-related symptoms which cause distress and functional impairment yet do not meet full diagnostic criteria for disorder according to DSM. PTSD symptoms are more likely to occur in young, low-income, females than any other group, with partial symptoms especially prevalent among pregnant women (up to 28.6%). Experiencing these symptoms during pregnancy is likely to lead to poor prenatal care, adverse pregnancy outcomes, and lasting effects in the offspring. Hormonal shifts in pregnancy can influence the expression of the stress response in women with PTSD, especially as it relates to arousal, which is a cardinal symptom of PTSD. It is not yet known how normal pregnancy changes in ovarian, placental, and hypothalamic pituitary adrenal (HPA) axis hormones modulate arousal. This project aims to measure baseline autonomic response, as assessed by the acoustic startle response (ASR), in pregnant women with PTSD symptoms, pregnant women with trauma exposure and no PTSD symptoms, and non-traumatized controls. For women with partial symptoms of PTSD, a novel brief psychotherapy will be tested for the potential to reduce PTSD symptoms, and we will evaluate whether the treatment has an effect on the arousal rates as measured by the acoustic startle paradigm. Participants will be recruited from a prenatal clinic that primarily serves low-income, inner city, minority women. This is a population known to have high rates of trauma exposure in their lifetimes and who are unlikely to seek out mental health care. All study procedures, including the administration of the acoustic startle paradigm and the delivery of the brief psychotherapy, will take place in the prenatal clinic. We hypothesize that compared to women in the two comparison groups, pregnant women (gestational age 12-16 weeks) with partial or full symptoms of PTSD will demonstrate greater magnitude of ASR, higher levels of placental CRF, and lower salivary cortisol awakening response. We also expect that significantly more pregnant women receiving 4 sessions of the brief treatment will show decreases in partial PTSD symptoms than women randomized to a wait-list control. Lastly, we predict that the magnitude of the ASR will decrease from pre to post treatment in pregnant women who participate in all 4 treatment sessions compared to women in the waitlist control and that the magnitude of the decrease in ASR will be correlated with the decrease in PTSD symptoms as measured by the PTSD Checklist. We will also explore whether PTSD symptoms during pregnancy and HPA axis and arousal dysregulation increase a woman's risk for an adverse pregnancy outcome as defined by either preterm birth, low birth weight, or pregnancy induced hypertension.